The present invention relates to mechanical resonators and measuring instruments, such as viscometers or other instruments for measuring attributes of materials such as fluid media
FIG. 1 shows a torsional resonant system consisting of two distinct but connected resonators; one resonator is formed by an inertial mass J1 and its associated shaft K1 and the other formed by an inertial mass J2 and its shaft K1. The two shafts are connected at their ends so that, when the resonators are tuned to the same frequency, a vibrational node is formed at the shafts"" junction,
In a practical arrangement it is necessary to physically support the resonator system in space. To prevent damping of the moving members, the most appropriate point of support is at any vibrational nodal position where there is zero or minimal displacement in resonance. Conventionally, a single support structure K3 is located at the junction of the two shafts as shown schematically in FIG. 1. However, if there is a slight imbalance of frequencies between the two resonator systems then there will be some displacement at the node and the rigidity of the support structure will influence the resonant characteristics of the overall system. Although frequency imbalance may be naturally expected to occur the complex involvement of mounting rigidity is undesirable.
Reducing the mounting stiffness by using a more compliant design and/or materials will diminish the effect of the stiffness of the structure K3 (as described in GB-2281621) but compromises structural strength and thus significantly limits practical use. This invention describes a resonator support structure which has the virtues of high compliance to virtually eliminate detrimental effects of K3 but to preserve structural strength for practical usage.
According to the invention a mechanical resonator system comprises two distinct resonators connected by a nexus and being capable of vibration in anti-phase with a first vibrational node in the region of the nexus and at least a second node, a compliant support in the region of the first node and a semi-rigid support in the region of the second node. Further features of the invention will be apparent from the following description of an exemplary embodiment.